This adds a new route "t"-flag that enables network address translation,
replacing the source address (and local port) of a forwarded packet to
one of the outgoing interface.
The state for a translation is kept in a new Translation structure,
which contains two Iphash entries, so it can be inserted into the
per protocol 4-tuple hash table, requiering no extra lookups.
Translations have a low overhead (~200 bytes on amd64),
so we can have many of them. They get reused after 5 minutes
of inactivity or when the per protocol limit of 1000 entries
is reached (then the one with longest inactivity is reused).
The protocol needs to export a "forward" function that is responsible
for modifying the forwarded packet, and then handle translations in
its input function for iphash hits with Iphash.trans != 0.
This patch also fixes a few minor things found during development:
- Include the Iphash in the Conv structure, avoiding estra malloc
- Fix ttl exceeded check (ttl < 1 -> ttl <= 1)
- Router should not reply with ttl exceeded for multicast flows
- Extra checks for icmp advice to avoid protocol confusions.
when making outgoing connections, the source ip was selected
by just iterating from the first to the last interface and
trying each local address until a route was found. the result
was kind of hard to predict as it depends on the interface
order.
this change replaces the algorithm with the route lookup algorithm
that we already have which takes more specific desination and
source prefixes into account. so the order of interfaces does
not matter anymore.
there appears to be confusion about the refresh flag of arpenter().
when we get an arp reply, it makes more sense to just refresh
waiting/existing entries instead creating a new one as we do not
know if we are going to communicate with the remote host in the future.
when we see an arp request for ourselfs however, we want to always
enter the senders address into the arp cache as it is likely the sender
attempts to communicate with us and with the arp entry, we can reply
immidiately.
reject senders from multicast/broadcast mac addresses. thats just silly.
we can get rid of the multicast/broadcast ip checks in ethermedium and
do it in arpenter() instead, checking the route type for the target to
see if its a non unicast target.
enforce strict separation of interface's arp entries by passing a
rlock'd ifc explicitely to arpenter, which we compare against the route
target interface. this makes sure arp/ndp replies only affect entries for
the receiving interface.
handle neighbor solicitation retransmission in nbsendsol() only. that is,
both ethermedium and the rxmitproc just call nbsendsol() which maintains
the timers and counters and handles the rotation on the re-transmission
chain.
no need to rlock ifc in targetttype() as we are called from icmpiput6(),
which the ifc rlocked.
for icmpadvise, the lport, destination *AND* source have to match.
a connection gets a packet when the packets destination matches the source
*OR* the packets source matches the destination.
rfc4861 7.2.2:
If the source address of the packet prompting the solicitation is the
same as one of the addresses assigned to the outgoing interface, that
address SHOULD be placed in the IP Source Address of the outgoing
solicitation.
this change adds ndbsendsol() which handles the source address selection
and also handles the arp table locking; avoiding access to the arp entry
after the arp table is unlocked.
cleanups:
- use ipmove() instead of memmove().
- useless extern qualifiers
ipv4local() and ipv6local() now take remote address argument,
returning the closest local address to the source. this
implements the standartized source address selection rules
instead of just returning the first local v4 or v6 address.
the source address selection was broken for esp, rudp an udp,
blindly assuming ifc->lifc->local being a valid v4 address.
use ipv6local() instead.
the v6 routing code used to lookup source address route to
decide to drop the packet instead of checking the interface
on the destination route.
factor out the route hint from Conv and put it in Routehint
structure. avoiding stack bloat in v4 routing. implement the
same trick for v6 avoiding second route lookup in ipoput6.
fix memory leak in icmpv6 router solicitation handling.
remove old unfinished handling of multiple v6 routers. should
implement source specific routes instead.
avoid duplication, use common convipvers() function.
use isv4() instead of memcmp v4prefix.
windows 7 just drops the default router when it tries to
probe for router reachability but gets a neighbor avertisement
from the router with the router bit clear.
so set the R-flag when sendra is active, which implies that
we are a router.
